Shelf stable meat analogues comprising glycerol and glucose

ABSTRACT

The invention relates to a method of manufacturing a texturised proteinaceous meat analogue having a relative water activity of less than about 0.8, comprising proteinaceous materials selected from the group consisting of defatted soy flour, soy meal, soy concentrate, cereal gluten (in vital or starch containing form) and egg white powder, edible binding and cross-linking compounds, and a humectant of glycerol and glucose, and the products thereof. The mixture is converted into hot lava, extruded and cooled.

FIELD OF THE INVENTION

The present invention broadly relates to the manufacture of edibleproteinaceous products, in particular texturised protein products(TPP's) for human and/or animal consumption. In particular, theinvention relates to a shelf-stable TPP of intermediate moisture and amethod and apparatus for the manufacture of same.

BACKGROUND OF THE INVENTION

The industrial manufacture of meat analogue products from protein-richprecursor materials, including plant based precursors such as cerealgrain protein (of wheat, rice, or maize; vital or with residual starch),defatted oil seed, cereal and bean flours, meals and derivatives. (e.g.defatted soy flour, soy protein concentrates, wheat flour), or animalbased precursors such as meat by-products obtained by mechanicalseparation, fish meal, dried egg white powder and others, alone or incombination, is a well-established practice. Extrusion cookingtechnology is the most widely used of different possible manufacturingmethods to obtain such meat analogues.

The general, state of the prior art with respect to such products andprocesses for their manufacture is surveyed in detail in patent documentNo. WO 00/69276, by Effem Foods. Pty Ltd. This document discloses amethod of manufacturing a texturised protein product that mimics theappearance of flaked fish meat, shredded chicken meat or other meatproducts, as well as an apparatus for manufacturing such product. Inparticular, the document discloses a suitable formulation for atexturised protein product that enables the TPP to be formed in ahigh-moisture, extrusion cooking process, and to be mechanicallyshredded into flakes that closely resemble an animal protein product intexture and structure, such as flaked fish meat or shredded chickenmeat.

However, the technology disclosed in WO 00/69276 does not provide a TPPthat is suitable for all desirable applications. For example, it isdesirable to include such “visually authentic” pieces as a directinclusion in ‘dry’ or semi-moist packeted pet foods (as compared tomoist, canned pet foods), in order to reinforce the impression to thepurchaser that the product contains ‘real’ fish or chicken. Therelatively high moisture levels of the product disclosed in WO 00/69276would prevent their direct inclusion in such dry or semi-moist packetedproducts, as their moisture content would impart a limited shelf life tothe overall product, reducing their commercial feasibility. Inclusion ofsuch TPP products in an unsterilised, packeted environment would belikely to lead to spoilage via the development of mould or otherspoilage organisms within a few hours of manufacture. In order to becommercially feasible, the shelf life of packeted products, which areusually not sterilized, needs to be at least nine months, and preferably12 months, thus making the inclusion of high-moisture TPP difficult.

An obvious solution to this problem would be to dry the TPP in order todecrease its relative water activity to <0.8 in order to significantlyreduce the activity of spoilage organisms. However, this wouldsignificantly increase the hardness of this type of TPP, thereby greatlydecreasing its acceptability to the animal.

In this document, the term ‘relative water activity’ is used accordingto the meaning it is usually accorded in the art, that being theproportional availability of the present water molecules to reactrelative to pure liquid water.

Reformulation of the TPP may be undertaken in order to reduce wateractivity, such as by increasing the cereal content. However, suchreformulations will tend to have deleterious effects on the texture andpalatability of the TPP, and may also adversely affect the ability ofprocessing equipment to effectively produce the TPP in the desired form.For example, general decreases in formulated moisture levels will leadto greater work being done by the extruder screw as the material passesthrough it. This results in greater heat development in the material,which may lead to expansion, or ‘puffing’ of the product. As this wouldtend to ruin the non-expanded, striated, meat-like appearance intended,such a solution is not desirable.

A common way to reduce water activity while maintaining product textureis to incorporate one or more humectant materials in the formulation.However, for the type of product described in WO 00/69276, i.e.high-moisture extruded TPP, it has been found that many of the commonhumectant systems do not provide a solution to the problem. Theincorporation of sugars at 12% by mass of the formulation, as used inother semi-moist pet foods, tended to cause blockages and productburning in the high-shear twin-screw extruders that are necessary forthe manufacture of this type of product.

Similarly, the use of a lower viscosity humectant material, such as asugar solution, resulted in an inability of the process to provide thecorrect ‘striated’ texture for the product. This is because lowerviscosity/higher fluid content feedstocks are not capable of producing atextured extrudate, especially for this type of extrusion.

Other liquid humectants, such as propylene glycol, are available forextending the shelf life of such TPP products. However, these materialsalso tend to compromise the texture of the product when added at thelevels necessary to produce the shelf-life extension sought.Furthermore, propylene glycol is not suitable for TPP that is to be fedto felines, as it is toxic for these animals. It also tends to produce aflavour taint that is undesirable.

Therefore, it is an object of the invention is to provide a TPP havingvisual and textural properties similar to those described in WO00/69276, but with a significantly extended shelf-life, such that itdoes not require further sterilisation processing. It is another objectof the invention to provide a process for the manufacture of same.

SUMMARY OF THE INVENTION

Accordingly, in a first aspect of the present invention, there isprovided a method for manufacturing a texturised proteinaceous meatanalogue product, having a relative water activity of lower than about0.8, said method including the steps of:

subjecting, in a food-extruder, a mixture containing about 20 to 80% byweight edible proteinaceous materials selected from the group consistingof predetermined mixtures of defatted soy flour, soy meal, soyconcentrate, cereal gluten (in vital or starch-containing form) and eggwhite powder; up to about 5% by weight of edible mineral binding andcross-linking compounds; and up to about 50% by weight: of an ediblehumectant system consisting of a mixture of glycerol and glucose ofpredetermined ratio; to mechanical pressure and added heat sufficient toconvert the mixture into a hot protein lava; and

extruding the protein lava through and from a temperature controlledcooling die which cools and increases the viscosity of the protein lavato obtain a cohesive, texturised, extrudate slab or ribbon in whichvapour-flashing is substantially inhibited.

Preferably, the product contains about 25% by weight glycerol and about5% by weight. of glucose. The presence. of these humectants allows theTPP to maintain a texture that is, soft enough to be acceptable to theconsumer, while reducing the water activity to-a level that allows ashelf life of at least 12 months in ambient conditions. Unexpectedly,this combination of liquid humectant ingredients does not produce adeleterious effect on product texture or on the ability of the equipmentto successfully process the materials. The water activity of the finalproduct can be advantageously set to between about 0.55 and about 0.68.

Preferably, the temperature of the product components in the extruder isminimised by using a twin-screw extruder with five barrel sections and ascrew speed in the range 300 rpm to 550 rpm, and even more preferablyabouts 500 rpm. The temperature of the molten lava is preferablyrestricted to <120° C.

Preferably, the solidified extrudate slab or ribbon is subjected tosuitable size-reduction techniques for producing extrudate shreds thatresemble in consistency and texture flaked or-shredded meat.

Preferably, the size reduction is performed by shredding in a hammermill having a cage plate with a plurality of elongate discharge openingsand a plurality of hammer bars hinged to discs attached to a rotatingshaft. Use of the hammer mill as described advantageously enables themanufacture of extrudate shreds that resemble, in consistency andtexture, flaked fish meat, shredded chicken meat or shredded red meat(such as beef or lamb).

In performing the above method, addition of real meat or meat by-productinto the TPP mass is an optional step to enhance flavor and to provideanimal protein contents. This addition may occur prior to, during orafter the step of subjecting the mixture to mechanical pressure andheat. Preferably, the addition of the meat product or meat by-productoccurs during the extrusion step. This real meat or meat by product maybe obtained from fish, poultry or from livestock (such as cattle orsheep).

Advantageously, the extrudate is transferred directly from the coolingdie to the hammer mill for shredding, as shredding or flaking theextrudate whilst the extrudate slab is still warm provides shreds orflakes of more authentic appearance. Therefore, typically, the timebetween extrusion and cutting should not exceed 5 minutes.

Preferably, the mixture referred to above has total moisture content ofbetween about 15% and about 40% by mass.

It will be understood that the extrudate can be conveyed as a continuousband or ribbon directly into the hammer mill, or it may be conveyed inshorter lengths or discontinuous portions.

A preferred formulation of the meat analogue product, which results inextrudate shreds that substantially mimic tuna fish flakes, that can beblended directly into a packeted pet food product, consists of: a dryingredient mixture, making up about 50% of extrudate mass, consisting ofabout 40% defatted soy flour, about 40% vital wheat gluten, about 0.5%nutritional vitamin supplements, about 8.5% mineral supplements, about2.0% flavouring agents, about 4.3% colouring agents and about 4.7%carbohydrate (all weight %); a humectant blend, making up about 30% ofextrudate mass, consisting of about 83% glycerol and about 17% glucose;and injected meat material, making up about 20% of extrudate mass,consisting of comminuted material derived from chicken, fish orlivestock.

As disclosed in WO 00/69276, a conventional hammer mill, which isgenerally employed to grind, particulate or pulverise dry, relativelyhard materials such as coal, grains, seeds and similar dry materials,can be employed with a modified screen in accordance with this aspect ofthe invention to shred the proteinaceous, plasto-elastically-resilient,and moisture-rich extrudate slab or ribbon into chunks or pieces thatclosely resemble in appearance those of shredded tuna fish meat orchicken meat, without otherwise adversely affecting the structure andtexturisation of the TPP shreds.

The cooling die may be adapted so as to form an extrudate slab or ribbonhaving any suitable cross-section (e.g. rectangular or circular).

A production line incorporating the inventive method may be arrangedsuch that continuous manufacturing of shredded TPP extrudate is achievedfrom metering of the dry ingredients and water into the extruder tometering the extrudate shreds into appropriate vessels for furtherprocessing. Alternatively, a further conveyor means can be disposedunderneath the hammer mill discharge chute for conveying the meatanalogue shreds towards further processing units of an integrated foodproduction line, (e.g. Ha canning station or the like).

In a further refinement, it has been found to be particularlyadvantageous in conducting the manufacturing process to employ aconveying and pressurising twin-screw extruder with 4 to 6 barrelsections that are individually temperature controlled, each sectionhaving a length to diameter ratio of approximately 4, as used in highmoisture extrusion cooking. Temperature settings at the individualbarrel sections during the manufacturing process will vary between 60and 150° C. and internal pressure between 3 and 8 MPa, at screw speedsof between 300 to 550 rpm.

In a second aspect, the present invention provides a shredded meatanalogue product manufactured in accordance with any one of theprocesses described above using the formulation of materials referred toabove.

Further features and advantages of the invention will be described inthe following in relation to preferred embodiments thereof by way of aspecific, non-limiting example.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The following non-limiting description of a preferred embodiment of theinvention is presented with reference the TPP product, and themanufacturing processes and equipment therefor, as described in detailin patent document No. WO 00/69276.

A TPP product having a fibrous striated structural matrix and resemblingtuna white-meat was prepared generally according to the process andformulation details given in Example 2. in the preferred embodimentdescription of WO 00/69276, except with the changes to formulation andprocess conditions outlined as follows:

The ingredients listed in Table 1 were weighed out as indicated there,milled through a hammer mill fitted with a screen of size 1.2-2 mm andpre-blended in a ribbon blender for 4 minutes. TABLE 1 Ingredient % bymass Defatted soy flour 40 Vital wheat gluten 40 Vitamins 0.5 Minerals8.5 Carbohydrate 4.7 Flavouring agents 2.0 Colouring agents 4.3

Added to this mix was a blend of humectants, consisting of 83% glycerolby weight and 17% glucose by weight. This blended mixture was then fedinto the hopper and metered into the extruder (Werner & Pfleiderer C58,fitted with 5 barrel sections) at a rate of 138 kg/hr. Comminutedtuna-derived material was injected into the molten material at a ratesuch that the overall mass-flow ratio of dry material:humectants:tunamaterial was approximately 5:3:2. The extruder screw speed was set at530 rpm. Temperatures of the barrels were regulated to the values listedin Table;2. TABLE 2 Barrel number Temp ° C. 1 20 2 50-60 3 70-80 4100-110 5 110-120

The dry precursor materials are plasticised and molten into a viscousextrudate as they are conveyed through the extruder barrel sections. Thehot melt is extruded through the breaker plate. The extrudate leavingthe breaker plate enters the cooling die channel member (cross-sectionaldimensions of 50 mm by 7 mm and a length of 400 mm), cooling water inlettemperature being set at about 5° C.

Extrudate product exiting the cooling die as a continuous slab wasanalysed and shown to have a moisture level of 25% by weight and a wateractivity of 0.68. The slab was then conveyed directly to the modifiedhammer mill. The product slab was cut and shredded into pieces of torn,non-uniform appearance, quite similar to canned white tuna pieces. Therotational speed of the hammer discs was set to 1800-2000 rpm, whilst ascreen with holes of a size of 50 mm by 7 mm was employed.

The shredded pieces obtained had an appearance similar to that ofshredded tuna meat. This material has a shelf life in excess of 12months in ambient conditions.

1. A method for manufacturing a texturized proteinaceous meat analogueproduct, said product having a relative water activity of lower thanabout 0.8 said method comprising the steps of: subjecting, in anextruder, a mixture containing about 20 to 80% by weight edibleproteinaceous materials selected from the group consisting ofpredetermined mixtures of defatted soy flour, soy meal, soy concentrate,cereal gluten and egg white powder; up to about 5% by weight of ediblemineral binding and cross-linking compounds; and up to about 50% byweight of an edible humectant system consisting of a mixture of glyceroland glucose in a predetermined ratio, to mechanical pressure and heatsufficient to convert the mixture into a hot protein lava; and extrudingthe protein lava through and from a temperature controlled cooling diewhich cools and increases the viscosity of the protein lava to obtain acohesive, texturized, extrudate slab or ribbon in which vapour-flashingis substantially inhibited.
 2. The method of claim 1, wherein saidmixture contains about 25% by weight glycerol and about 5% by weight ofglucose.
 3. The method of claim 1, wherein said meat analogue producthas a relative water activity of between about 0.55 and about 0.68. 4.The method of claim 1, wherein said extruder is a twin-screw extruderwith between four and six barrel sections and a screw speed operating inthe range 300 rpm to 550 rpm.
 5. The method of claim 4, wherein saidextruder has five barrel sections and said screw speed is about 500 rpm.6. The method of claims 5, wherein each extruder barrel section has alength to diameter ratio of about
 4. 7. The method of claim 1, whereinthe temperature of said protein lava is restricted to less than about120° C.
 8. The method of claim 1, wherein the solidified extrudate slabor ribbon is further subjected to suitable size-reduction techniques forproducing extrudate shreds that resemble in consistency and textureflaked or shredded meat.
 9. The method of claim 8, wherein saidsize-reduction includes shredding in a hammer mill.
 10. The method ofclaim 9, wherein said hammer mill includes a cage plate with a pluralityof elongate discharge openings and a plurality of hammer bars hinged todiscs attached to a rotating shaft.
 11. The method of claim 10, whereinthe extrudate is transferred directly from the cooling die to the hammermill.
 12. The method of claim 1, further including the step of addingmeat based product into said mixture.
 13. The method claim 12, whereinsaid meat-product is added directly to said protein lava.
 14. The methodof claim 14, wherein said mixture has a total moisture content ofbetween about 15% and about 40% by mass.
 15. The method of claim 1,wherein said mixture includes: a dry ingredient blend, said dryingredient blend making up about 50% of meat analogue product mass andincluding (by mass) about 40% defatted soy flour, about 40% vital wheatgluten, about 0.5% nutritional vitamin supplements, about 8.5% mineralsupplements, about 2.0% flavouring agents, about 4.3% colouring agentsand about 4.7% carbohydrate; a humectant blend, said humectant blendmaking up about 30% of meat analogue product mass and including about83% glycerol and about 17% glucose by mass; and meat based material,said meat based material making up about 20% of extrudate mass andconsisting of comminuted material derived from one or more animalsselected from the group consisting of poultry, fish, ovines, bovines andporcines.
 16. (canceled)
 17. The method of claim 1, wherein the cerealgluten is in vital or starch-containing form.
 18. A meat analog product,said product having a relative water activity of lower than about 0.8,said product produced by a method comprising the steps of: subjecting,in an extruder, a mixture containing about 20 to 80% by weight edibleproteinaceous materials selected from the group consisting ofpredetermined mixtures of defatted soy flour, soy meal, soy concentrate,cereal gluten and egg white powder; up to about 5% by weight of ediblemineral binding and cross-linking compounds; and up to about 50% byweight of an edible humectant system consisting of a mixture of glyceroland glucose in a predetermined ratio, to mechanical pressure and heatsufficient to convert the mixture into a hot protein lava; and extrudingthe protein lava through and from a temperature controlled cooling diewhich cools and increases the viscosity of the protein lava to obtain acohesive, texturized, extrudate slab or ribbon in which vapour-flashingis substantially inhibited.
 19. The meat analog product of claim 18,wherein said mixture contains about 25% by weight glycerol and about 5%by weight of glucose.
 20. The meat analog product of claim 18, whereinsaid meat analogue product has a relative water activity of betweenabout 0.55 and about 0.68.
 21. The meat analog product of claim 18,wherein the solidified extrudate slab or ribbon is further subjected tosuitable size-reduction techniques for producing extrudate shreds thatresemble in consistency and texture flaked or shredded meat.
 22. Themeat analog product of claim 18, wherein the cereal gluten is in vitalor starch-containing form.